Add new entry to CHANGELOG for version 6.0.0

Author: mokagio

CHANGELOG.md

@@ -34,6 +34,24 @@ _None._
 
 ### Breaking Changes
 
+_None._
+
+### New Features
+
+_None._
+
+### Bug Fixes
+
+_None._
+
+### Internal Changes
+
+_None._
+
+## [6.0.0](https://github.com/wordpress-mobile/WordPressKit-iOS/releases/tag/6.0.0)
+
+### Breaking Changes
+
 - Re-implement a few reader model types in Swift. [#556, #557, #558]
 - Implicityly Unwrapped Optionals in some model types are removed. [#569]